R. C. Sproul in the article, The People of God, does not believe in Replacement theology but that there has always been one people of God. In the O. T. it was Israel and in the N.T. it is the church who is the true Israel of God. His conclusion is the similar to Replacement Theology in that the church is not a separate people of God and all the OT promises to Israel must be allegorized to be fulfilled today by the church. Sproul also makes the unfounded accusation that because we believe in two peoples of God we believe in two ways of salvation. Notice there is no documentation for this caricature. Here is his article:
“Once you were not a people, but now you are God’s people; once you had not received mercy, but now you have received mercy” (1 Peter 2:10).
In our day there exists much confusion regarding the identity of the true people of God. Some conceive of the church as a mere parenthesis in the plan of God — an afterthought brought about by ethnic Israel’s rejection of Christ. For these people, the authentic people of God are the physical descendants of Abraham.
Others say that the church has replaced Israel in the plan of God. Older proponents of this view have tended to say that with the church, God has exchanged the Gentiles for the Jews.
While both groups of people would affirm the necessity of Christ for salvation, neither is the biblical view. Either way, the fundamental unity of the people of God across the ages is denied. Whether it is said that the church is an afterthought or that the church replaces Israel, both views implicitly affirm that there are two different ways of salvation, one for the Jews and one for the Gentiles
However, the Bible teaches that there is but one people of God and only one way of salvation. In 1 Peter 2:9, Peter calls his mostly Gentile audience “a royal priesthood, a holy nation, and a people for his own possession.” These are all terms used for the nation of Israel in the Old Testament (Ex. 19:5–6; Isa. 43:20–21), and Peter applies them to the church because the church is the true Israel of God.
The biblical view (which is sometimes mistakenly called “replacement theology”) does not say that the church “replaces” Israel. Rather, it affirms that true Israel always was, always is, and always will be comprised of those who trust in Christ alone for salvation. This is plain from 1 Peter 2:10. The Gentiles, who were formerly not God’s people, are now God’s people because they have trusted in the Messiah and because they worship Israel’s true King.
Old covenant believers were likewise able to be the people of God because they were in Christ. Though they lived before the Son became incarnate, they looked forward to the day in which He would come, and they trusted in Him (John 8:56). Their example likewise shows us that the true Israel of God has always been comprised of those who love and serve the Messiah.
That the church is the Israel of God does not mean that every church member has authentic faith. Throughout history, the visible church has always included those who are not true believers because of their inauthentic faith (Rom. 9:6–7). However, in Christ, God is fulfilling all of the promises made to Israel. As the people of God, we must fulfill the task of Israel and proclaim God’s excellency (1 Peter 2:10). Seek to do this in whatever you do.
Three reasons for believing “the Israel of God” is the believing Jewish remnant within the church and not Israel’s replacement or the same as the OT people of God.
The first reason is grammatical in Galatians 6:16
The common use of the kai is the continuative or conjunctive and is the primary meaning which should be used. Charles Ryrie speaks of the emphatic use of kai as in Mark 16:7 and Acts 1:14 which also draw a distinction between groups. Kai is used over 9000 times as simple conjunction or “and.”
The second reason is exegetical in Galatians 6:16
“Exegetically the view is sound, since ‘Israel’ has its uniform Pauline ethnic sense. And further, the apostle achieves a very striking climatic conclusion. Drawing near the end of his ‘battle-epistle’ with its harsh and forceful attack on the Judaists and its omission of the customary words of thanksgiving, Paul tempers his language with a special blessing for those faithful believing Israelites who, understanding the grace of God and its exclusion of any human works as the ground of redemption” (Essays in Honor of J. Dwight Pentecost, page192).
The third reason is theological in Galatians 6:16
What Paul presents in Galatians 6:16 is consistent with his teaching in Romans 9 and 11 that there are two groups in the church: Gentiles and ethnic Jews. In Romans 9, Paul describes Israel’s past (not the church). In Romans 10, Paul presents Israel’s present (not the church 10:1). In Romans 11, Paul predicts Israel’s future (11:25-26). God is not through with Israel.